Spatial perception and sensory-guided movements are thought to depend upon several different neural representations of the external environment. Recent studies of the oculomotor system suggest that there are at least three neural representations of a visual target to which a saccade is made: representations in retinal, spatial (head or body) and motor coordinates. The major purpose of the experiments outlined in this proposal is to systematically search for a neural representation of the visual environment that is organized in spatial coordinates. The techniques to be used (chronic unit recording, microstimulation and mapping of metabolic activity) were selected to maximize the likelihood of identifying regions of the CNS that are involved in coding the spatial location of objects in the external environment. Other experiments are proposed that will a) obtain a behavioral estimate of the duration and precision of memory for the spatial location of a visual target; b) study the relationship between neuronal activity in the primate superior colliculus and performance on this spatial memory task; and c) examine the neural mechanisms involved in selecting one of several spatially-localized targets as the goal for a motor response. Findings obtained from these studies should contribute, significantly, to our information about the brain areas involved in neurological disturbances of spatial perception and spatially oriented behavior.